A Juniper firewall can display data with the tcpdump command:

% tcpdump -i ge-0/0/0
% tcpdump -i vlan10

However, if the interface or the VLAN is assigned to a routing instance, the traffic is not captured. Is there a way to do it ?

1 Answer 1


This works fine on the lower-end SRX models - try using the layer 3 interface bound to your VLAN eg:

tcpdump -i vlan.10

My configuration looks like this:

routing-instances {
        instance-type virtual-router;
        interface vlan.10;
vlans {
    v10-TEST {
        vlan-id 10;
        l3-interface vlan.10;

Bear in mind that you won't be able to see traffic that isn't directed at the RE (eg: destination IP address of vlan.10 interface). You also won't be able to see ICMP traffic, as this is processed via the PFE, rather than the RE.

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